Polymer alloys of high-molecular-weight benzoxazine and epoxy resin

Novel polymer alloys were prepared by curing the mixture of a high-molecular-weight benzoxazine (B-oda) that was synthesized from 4,4′-oxydianiline (oda), bisphenol-A, and formaldehyde and a typical epoxy resin prepolymer, epoxy-terminated copolymer of bisphenol-A and epichlorohydrin, up to 240°C. It was confirmed by differential scanning calorimetric and infrared (IR) investigations that the novel alloys had ether linkages that was formed by the reaction between the phenolic hydroxyl groups formed from the thermal ring-opening polymerization of B-oda and the epoxy groups of the epoxy resin. The properties of the alloy films were compared with polybenzoxazine (PB-oda), the pristine polybenzoxazine obtained by curing B-oda without the epoxy resin. The alloy films were more flexible and were found to have higher glass transition temperatures (Tgs) from the dynamic mechanical analyses. From the IR analyses of the films, the polymer alloys were found to have higher amount of intermolecular hydrogen bonding compared with the pristine PB-oda. It was suggested that this increase of the hydrogen bonding was the cause of the higher T gs of the polymer alloys.